1. Field of the Invention
The present invention relates to an integrated circuit package.
2. Background Information
Integrated circuits are typically assembled to a package that is mounted to a printed circuit board. There have been developed many types of integrated circuit packages including quad flat pack (QFP), ceramic pin grid array (PGA) and ball grid array (BGA) packages.
QFP packages contain a metal lead frame that has a plurality of individual leads which extend from a center die paddle. The die paddle supports the integrated circuit. The integrated circuit has a number of bond pads that are wire bonded to the individual leads. The integrated circuit and a portion of the lead frame are encapsulated with an injection molded plastic housing. QFP packages are relatively simple to assemble and inexpensive to produce. Unfortunately, QFP packages have a relatively high lead to lead spacing so that the density of the package pins is relatively low. It is generally desirable to have a high pin density to provide a large number of signal lines in a small amount of space. Additionally, the outer plastic housing of a QFP package has a low coefficient of thermal conductivity. QFP packages therefore do not efficiently remove heat generated by the integrated circuits. Consequently, QFP packages typically house relatively low power devices.
PGA packages include a plurality of pins that extend from a housing which encloses an integrated circuit. The pins of the package are mounted to an external printed circuit board. PGA package housings are typically constructed from a ceramic material, or a plastic/printed circuit board process, which create relatively high pin densities.
PGA packages typically include heat slugs and heat sinks that efficiently remove heat from the integrated circuit. Consequently, high powered integrated circuits such as microprocessors are typically packaged within PGA packages. Unfortunately, PGA packages are more expensive to produce than QFP products.
BGA packages have a plurality of solder balls that are attached to a substrate. The substrate may be constructed from ceramic or printed circuit board processes. Like PGA packages, BGA's provide high pin densities and may include a thermal element to remove heat generated by the integrated circuit. Unfortunately, BGA packages are also relatively expensive to produce.
There is always a desire to increase the memory and I/O busses of a system. The memory bus runs from a package that contains a microprocessor to a package(s) that contains a memory device(s). The packages are typically coupled together by a motherboard. Present packages typically provide leads, pins or solder balls in two dimensional arrays. The two dimensional arrays create variations in signal lengths between packages. It is desirable to provide equal signal paths for each data signal to minimize the slew between signals. Excessive signal slew may create data corruption, particularly for high speed busses. It would be desirable to provide an integrated circuit package which is thermally efficient, inexpensive to produce, and minimizes the difference in signal lengths between signal lines.